Ciphering machine

ABSTRACT

This invention relates to a ciphering machine for ciphering text in clear produced in binary form by superimposing every text in clear character signal with a variable ciphering signal. Such a machine comprises a number of electric devices stepped in parallel with cyclic operations, for example shift registers, the cycles being mutually different, said devices being formed, for example, by chains or rows of mutually different numbers of bistable flip-flops. The initial states of said flip-flops so were set according to a scheme of preferably random choice that the states of flip-flops stepped in parallel in every column in the different shift registers together define a ciphering character. These column characters, thus, automatically change their nature as soon as a shift register has completed a cycle.

United States Patent [7 2] Inventors Bengt Florin Hagersten; KaleviLoimaranta, Mattby, Finland [21] Appl. No. 805,624 [22] Filed Mar. 10,1969 [45] Patented Jan. 19, 1971 [7 3] Assignee AB Transvertex Varby,Sweden a Swedish Joint Stock Company [54] CIPHERING MACHINE 6/1902 HenzePrimary Examiner-Rodney D. Bennett, Jr. Assistant Examiner-Malcolm F.Hubler AttorneySommers & Young ABSTRACT: This invention relates to aciphering machine for ciphering text in clear produced in binary form bysuperimposing every text in clear character signal with a variableciphering signal. Such a machine comprises a number of electric devicesstepped in parallel with cyclic operations, for example shift registers,the cycles being mutually different, said devices being formed, forexample, by chains or rows of mutually different numbers of bistableflip-flops. The initial states of said flip-flops so were set accordingto a scheme of preferably random choice that the states of flip-flopsstepped in parallel in every column in the different shift registerstogether define a ciphering character. These column characters, thus,automatically change their nature as soon as a shift register hascompleted a cycle.

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SHEET 2 UF 3 T2 A B CIPI-IERING MACHINE It is previously known toproduce these ciphering signals changed constantly for every characterby means of a set of toothed wheels with a different number of teeth(preferably a prime number) which are mounted on the same shaft and arein driving connection with respective separately movable toothed wheelshaving the same number of teeth. At this second set of toothed wheelsevery tooth represent a binary bit, and the aligning teeth in the entireset of toothed wheels define a character formed by corresponding binarybits. Said second set of toothed wheels, thus, defines an manycharacters as there are teeth along the wheel circumference. At thebeginning,-the bits forming said characters are chosen at random. If thetoothed wheels of the first set (having a different number of teeth) arestepped simultaneously one tooth at a time, it is obvious that, when thedriving toothed wheel with the lowest number of teeth has been steppedthrough one entire revolution, the teeth then aligning in the driven setof toothed wheels will represent combinations of binary bits, i.e.characters, other than the original ones. The combinations are changedadditionally when the drive wheel with the next to lowest number ofteeth has completed its cycle, a.s.o. If, for example, the numbers ofteeth of the drive wheels are prime numbers, it is understood that thesame combinations (characters) as the original ones will not be obtainedunless the set of drive wheels has been stepped a number of steps whichis equal to the product of the respective number of teeth on the wheelscomprised in the set. I

Of the peripherally moving characters one character is selected forevery ciphering operation, which character corresponds to a row ofaligning teeth, either along one and the same reference line or with asystematic shifting between different lines in order to renderunauthorized deciphering still more difficult.

The ciphering character obtained (in form of a signal) is superimposedto the simultaneously stepped character in clear so as to form theciphered character.

The arrangement described above, however, involves severaldisadvantages.

From a purely ciphering point of view it shows the restriction that theaforesaid systematic change of characters in the peripheral series ofcharacters for purely practical reasons hardly can be carried out forcharacters (tooth rows) other than such located relatively closely.Consequently, the possibilities of changing existing in reality betweenthe total of characters located along all of the wheel circumference isutilized only to a small fraction.

These shortcomings are overcome by the ciphering machine according tothe invention which is characterized in that it comprises an arrangementadapted at every ciphering moment automatically to select one or some ofa number of selectable flip-flop columns in the flip-flop array and totransfer the signals corresponding to the flip-flop state in question toan adding device for forming the ciphering signal to be superimposed tothe text in clear signal.

One embodiment of the invention is described below with reference to theaccompanying drawings wherein:

FIG. 1 shows a basic diagram for a ciphering machine according to theinvention;

FIGS. 2 and 3 show wiring diagrams for two examples,

respectively, of character selectors comprised in the machine;

and

FIG. 4 shows the wiring diagram for a type for adding circuits alsocomprised in the machine.

FIG. 1 shows in this embodiment four shift registers S,,, S,,, S and 8.each of which comprises a chain of bistable flip flops, which here areshown merely schematically as clocked.

The number of flip-flops varies from one chain to another. The shiftregister 8 for example, which is represented in the FIG. by theuppermost row of flip-flops, comprises 13 flipflops a1 a 13. The shiftregister 8,, representing the second row comprises l2 flip-flops bl-bl2, and in an analogous manner the shift registers S and Srespectively, formed by the third and fourth row of flip-flops comprisel l and I0 flipflops cl cll and dl--dl0, respectively. 1

In every chain the outlet of one flip-flop is connected in a usual wayto the inlet of the next following flip-flop in such a manner, that uponstepping the register one the information in ever flip-flop in saidchain is shifted forward'one step. In the FIG. also is shown the lastflip-flop in every chain connected to the first flip-flop in the samechain in order to form a closed step cycle.

From the beginning, all of the flip-flops are given, for example bypunched cards, conditions preferably chosen at random. For the sake ofclearncss, however, the arrangement for this feed of information has notbeen included in the FIG. nor are the usual drive circuits for theshiftings shown.

The registers are intended to be stepped in parallel, i.e. theinformation bits in the first column kl of flip-flops a1, bl, cl and d1are transferred to the flip-flops 112-112 of the second column k2, andthe contents of the latter is transferred to the flip-flops a3--d3 ofthe third column, and so forth. Every flipflop column defines acharacter, which in this case comprises four bits. Owing to thedifference in length of the cycles of the shift registers the bits fedin from the beginning into, for example, the first column kl will bestepped unchanged to the last flip-flop 1110- of the register 8corresponding to column kl0. At a further parallel stepping the shiftregister 8,, starts a new cycle with the beginning in k1 where theoriginal bit in the flip-flop d1 returns, but the remaining bits in klare replaced by the bits in the flip-flops al3, H2, and 011,respectively, said bits being originally present in flip-flop a4, b3,and c2 of the registers S,,S At the next stepping the register S startsa new cycle with the beginning in kl, which now in addition to theoriginal bit in the flip-flop cl includes the new bits from 013, 112 andd10. This cycle is repeated in an analogous manner for the remainingregisters S and S,,. It is understood that the original bit combinationsdo not appear again unless a number of steps equal to the product of thestep number of the four shift registers have been stepped.

In the following the arrangement is described which is used forselecting the character i.e. the bit combination in a column, to beutilized for ciphering a character in clear in the form of a pulse fedsimultaneously with the stepping of the shift registers.

For this purpose a number of character selectors are provided, in thiscase four in number, viz. T1, T2, T3 and T4. Every character selectorhas four pairs of inlets i 1-1'4, which are connected in parallel withthe corresponding inlets of the other character selectors and adapted tobe connected to four pairs of flip-flop outlets of an arbitrary columnvia a switch (system selector) V not described in detail. In thefollowing argumentation the selectors are assumed, as indicated in theFigure, to be connected to the flip-flops a1-dl, respectively, of thecolumn kl via conductor pairs LlL4.

The outlets Ul-U4, respectively, of every character selector T1, T2, T3and T4 are connected to the one inlet of-in this case two-AND-gates 01and 05, and 02, 06; 03, 07; and 04, 08, respectively. The other inlet ofevery gate 0l--08 is connected to the outlet of an adding circuit AlA8,which like the character selector has four pairs of inlets, each pairbeing connected to the respective four flip-flop outlet pairs of itscolumn via the switch V. In the embodiment shown the switch is assumedso be set that the adding circuits Al-A8 are connected to the flip-flopcolumns k2-k9 straight above them in the FIG. The outlets gl-gB,respectively, of the gates 01-08 are all connected (but for the sake ofclarity shown only for the outlet g8) to a first 6v on a final addingcircuit SA, to the other inlet kl of which a binary coded signal inclear is fed in a way not described in detail synchronously with thestepping of the shift registers Sl-S4. From the outlet ch of the addingcircuit SA then the signal is taken out which is superimposed with thecharacter content of the column in question, i.e. the ciphered signal.

Before describing the mode of operation of the above arrangement, itbriefly shall be dealt with the construction of the character selectorsTl-T4 and adding circuits A1A8, with reference to FIGS. 24 showingembodiments of the construction of these arrangements. As appears fromFIGS. 2 and 3 the character selectors T1 and T2 are built up of the samecomponents, i.e. AND-gates G1-G5, but the internal connections are madedifferent in order to give every character selector its own specialnature. In FIG. 2, thus, the gate pairs G1, G2 and G3, G4 are shownconnected in like manner with respect to the respective inlet pairs i 1,i2, i3, i4, in that in both of the gate pairs G1, G2; G3, G4 theO-conductor in the lefthand inlet pair [1 and i3, respectively, extendsto the l-inlet on the right-hand gate G2 and G4, respectively, in thepair, and the l-conductor in the right-hand inlet pair i2 and i4respectively, extends to the O-inlet on the left-hand gate G1 and G3,respectively, in the pair. In FIG. 3 the relation is the same as regardsthe left-hand gate pair G1, G2 while at the right-hand gate pair G3, G4the O-conductor in the left-hand inlet pair i3 extends to the O-inlet onthe right-hand gate G4, and the O- conductor in the right-hand inletpair i4 extends to the O-inlet on the left-hand gate G3.

By these two basic type connections represented by the lefthand andright-hand gate pair, which may be designated by A and B, theconnections of the two remaining character selectors T3 and T4 areobtained in that T3 is built up of a left-hand par part of B-type and arighthand part of A-type, and T4 is built up of a left-hand part B and aright-hand part also of B- type.

A Table of the buildup of the four character selectors T1- -T4 and thebit combinations deductible from FIGS. 2 and 3) at the inlets in il-i4causing outsignal from the character selector in question, is shownbelow.

FIG. 4 shows the buildup of the adding circuits A1-A8 which are ofmutually entirely equal nature and built up in a conventional way withunit circuits connected to each other of the type as framed in FIG. 4. Amore detailed description appears not necessary.

A simple example may illustrate the mode of operation of the cipheringmachine described above.

It is assumed that in a certain moment during the continued stepping ofthe field of columns k1-k9 in column kl the bits 1 0 O are found in therespective flip-flops ald1. This character signal is fed via respectiveconductor pairs Ll-L4 to the inlets il-i4 of all character selectorsTlT4. Hereby only the character selector T3 (according to the Tableabove) gives an outsignal to associated AND-gates 03 and 07. At thesecond inlets of these gates-as at the second inlets of all remaininggatesa signal is available by assistance of the adding circuit A3 (A7,respectively) which represents the total of the character bits in columnk4 (and column k7). These bits are, for example, assumed to be 1 1 0 l(and O 0 1 1). The total b1 then is 1 (0, respectively). As theoutsignal of the character selector opens gate 03 (07, respectively),this l-signal (0signal, respectively) passes through to the inlet on thefinal adding circuit SA in order there to be superimposed to the text inclear impulse arriving at the same time. (The O-signal possibly can beused as a second superimposing pulse).

At the next stepping of the shift registers a character selectordetermined by the new bit combination in the flip-flop column k1 willopen the passage for a new signal from a corresponding column, aso. Forevery new stepping, thus, a jump" forward or back of the practicallyalways entirely available field of all informations in the flip-flopchains of the different shift registers is obtained. This renderspossible a many times greater utilization of the total charactervariations in the information field than it is possible at the mechanicdesigns of ciphering machines.

The fact that in the example shown only four character selectors arerequired together with the four flip-flops in every column, has itsreason in the circumstance that both the character itself and its poleswitching are allowed to act upon the character selectors in theirdesign shown.

In like manner as at the known ciphering arrangements operating withbinary code, the deciphering is carried out simply by superimposing theciphered signal pulses with the same series of pulses as used at theciphering operation. Owing to the special nature of the binary system,the text in clear is restored.

The invention is not restricted to the embodiment described above, butvarious modifications thereof can be imagined, particularly with respectto the number of shift registers and the relation between their cycles.

The invention in principle is not bound to the use of shift registers,but also other electric arrangements with cyclic operations can beimagined, such as binary counters with associated logic circuits.

The application field of the machine, furthermore, can be widened to alarge extent by making the cycles of the electric arrangements inquestion adjustable.

We claim:

1. In ciphering machine for ciphering text in clear produced in binaryform, by superposing every text-in-clear character signal with avariable ciphering signal, comprising a plurality of electric devicesstepped in parallel, said devices each having a different and repetitiveoperative cycle and forming an array of parallel rows of a differentnumber of bistable flipflops, the initial states of which are setaccording to an arbitrary scheme so that the states of flip-flopsstepped in parallel define together, in every flip-flop column of saidarray, a ciphering character, whereby said column charactersautomatically change their bit composition every time a row offlip-flops has completed a cycle and starts a new one; the improvementcomprising means, responsive to the present contents of a flip-flopcolumn in a preselected reference position, to select, at each cipheringmoment or step, at least one of the remaining flip-flop columns in theflip-flop array, as determined by said contents, and to transfer thesignals corresponding to the states of the selected flip-flops to anadding device for producing said ciphering signal which is to besuperposed on the text-in-clear signal.

2. A machine according to claim 1, where the means for selecting atleast one certain flip-flop column comprises a plurality f of characterselectors individually associated with a different one of said remainingflip-flop columns, and each of said character selectors having aplurality of inputs of the same number as that of the flip-flop rows,the inputs of all of said character selectors being connected inparallel to the cor responding outputs of the flip-flops in the columnof said reference position, and each of said character selectors havingits output connected to one input of an AND-gate, the second input ofwhich is connected to the output of an adding circuit, said addingcircuits having their respective inputs connected with the outputs ofthe flip-flops in the associated columns such, that for a certaincharacter in said reference position column only one character selectoris activated to supply an output signal to its AND-gate, at the secondinput of which the output signal from its adding circuit is alwayspresent, for effecting an output signal from said AND-gate, representingsaid ciphering signal.

3. A machine according to claim 2, wherein each of the characterselectors comprises a system of AND-gates having its respective inputconnected to the output of the flip-flop of said reference positioncolumn in such a manner that an output signal from the gate system isobtained only in response to certain definite characters in saidreference column.

4. A machine according to claim 2, wherein a switch is placed betweenthe outputs of the flip-flop columns and the associated adding circuitsfor enabling shifting of the connections between said flip-flop columnsand the character selectors.

1. In ciphering machine for ciphering text in clear produced in binaryform, by superposing every text-in-clear character signal with avariable ciphering signal, comprising a plurality of electric devicesstepped in parallel, said devices each having a different and repetitiveoperative cycle and forming an array of parallel rows of a differentnumber of bistable flip-flops, the initial states of which are setaccording to an arbitrary scheme so that the states of flip-flopssTepped in parallel define together, in every flip-flop column of saidarray, a ciphering character, whereby said column charactersautomatically change their bit composition every time a row offlip-flops has completed a cycle and starts a new one; the improvementcomprising means, responsive to the present contents of a flipflopcolumn in a preselected reference position, to select, at each cipheringmoment or step, at least one of the remaining flip-flop columns in theflip-flop array, as determined by said contents, and to transfer thesignals corresponding to the states of the selected flip-flops to anadding device for producing said ciphering signal which is to besuperposed on the text-in-clear signal.
 2. A machine according to claim1, where the means for selecting at least one certain flip-flop columncomprises a plurality f of character selectors individually associatedwith a different one of said remaining flip-flop columns, and each ofsaid character selectors having a plurality of inputs of the same numberas that of the flip-flop rows, the inputs of all of said characterselectors being connected in parallel to the corresponding outputs ofthe flip-flops in the column of said reference position, and each ofsaid character selectors having its output connected to one input of anAND-gate, the second input of which is connected to the output of anadding circuit, said adding circuits having their respective inputsconnected with the outputs of the flip-flops in the associated columnssuch, that for a certain character in said reference position columnonly one character selector is activated to supply an output signal toits AND-gate, at the second input of which the output signal from itsadding circuit is always present, for effecting an output signal fromsaid AND-gate, representing said ciphering signal.
 3. A machineaccording to claim 2, wherein each of the character selectors comprisesa system of AND-gates having its respective input connected to theoutput of the flip-flop of said reference position column in such amanner that an output signal from the gate system is obtained only inresponse to certain definite characters in said reference column.
 4. Amachine according to claim 2, wherein a switch is placed between theoutputs of the flip-flop columns and the associated adding circuits forenabling shifting of the connections between said flip-flop columns andthe character selectors.